This example of this expression has nothing to do with cocaine. It refers to the practice of enlightening one's own olfactory senses by inserting one's nose into the posterior orifice of another person or persons. Could be refered to as brown nosing, but does not carry the same reasoning behind the act ifself. It is purely for sensual pleasure.

Cheryl thinks I enjoy going down on her , but I'm really snortin crack while I'm eatin the kootch. She was puzzled when I mentioned that she'd had chineese last night. I love sniffin that butt just after she's taken a fresh dump.